It should be possible to create thicker walls like in Stronghold Crusader 2.

How is that possible?

https://github.com/wraitii/0ad_grand_strat Grand Strategy mod/mode.

Transport troops whit trains, is optional. My idea is to use Bézier curve for generating the mesh and other stuff, we can reuse the camera path for that xd. It will be "easier" for the cart/locomotive/railcar to follow the Bézier curve's direction vector (I think that's what it's called—correct me if I'm wrong). So no pathifnding calculation

I heartily agree with the last part, but note that using bows to shoot over one's own soldiers is AFAIK a historically attested practice. So not something we should forbid. And I mean, shooting over one's own melee soldiers was probably done to shoot on the soldiers engaging in melee with such melee soldiers...